SSL_set_fd - connect the SSL object with a file descriptor
int SSL_set_fd(SSL *ssl, int fd); int SSL_set_rfd(SSL *ssl, int fd); int SSL_set_wfd(SSL *ssl, int fd);
When performing the operation, a socket BIO is automatically created to interface between the ssl and fd. The BIO and hence the SSL engine inherit the behaviour of fd. If fd is non-blocking, the ssl will also have non-blocking behaviour.
If there was already a BIO connected to ssl,
The following return values can occur:
SSL_get_fd(3), SSL_set_bio(3), SSL_connect(3), SSL_accept(3), SSL_shutdown(3), ssl(3) , bio(3)